Each Yellow onion plant produces a singular edible bulbous root. The root forms a layered paper-like, copper-hued skin wrapped around its creamy white translucent, firm and succulent ringed flesh. Its high sulfur content makes it robust and sharp in both aroma and flavor.
The onion is a cool season vegetable yet it is grown and harvested year-round.
The Yellow onion, scientific name A. cepa, and member of the Allium family, is classified as a storage onion. It is also one of the most pungent varieties of onions, due its potency of sulfenic acids, highly reactive volatile sulfur compounds. Once the onion is opened, these acids release sulfuric acid gas, causing burning sensations in the eyes and forcing tears, a notorious onion trait.
Onions are divided into two categories: sweet onions and cooking onions. Sweet onions are best suited for fresh eating as they have higher moisture content equaling a shorter shelf life and a tendency to mold. Cooking onions have a longer shelf life. These are the storage onion varieties that can be stored at room temperature in a dry dark location. Yellow onions are the most common cooking onion utilized in cuisines throughout the world. Fresh eating should be avoided as the Yellow onion's pungency will linger long in raw form and dominate any companion ingredient. Yellow onions are the ubiquitous soup and stock onion. They can also be dry-roasted, sautéed, grilled, caramelized and braised.
The onion is one of the oldest cultivated vegetables and is considered to be native to Central Asia. It has been cultivated since ancient times in the Middle East and India. It is now the most widely cultivated and distributed allium in the world, adapting to a variety of climates from cold to temperate, semi-tropical and dry. Yellow onions start forming bulbs when the days are longer and the soil warms to 60 degrees fahrenheit. Mature Yellow onions are ready for harvesting when the green top withers, falls over and starts to turn brown.